1. Field of the Invention
This invention relates to a holder for a tool such as a tap, an end mill, a drill, an internal cutting tool, or an abrasive grindstone.
2. Descripyion of Prior Art
In machining by a machine tool such as a milling machine, a boring machine, a lathe or a polishing machine, the working accuracy is influenced much by the presence or absence and the magnitude of imbalance in weight, in a circumferential direction, of a rotary shaft (that is, a spindle) of a machine tool, a rotating tool or the like. Therefore, in machining of the type mentioned, it is important to reduce the imbalance of a rotary shaft and a rotating tool as much as possible in order to raise the working accuracy.
As one of tool holders which can adjust a rotary shaft and a rotating tool against an imbalance, a tool holder is available wherein a holder body having a first section of a truncated conical shape to be attached to a machine, a second section in the form of a bar coaxially exteding from the first section and a flange provided at a boundary portion between the first and second sections is used and balancing means is attached to the flange (U.S. Pat. Nos. 5,096,345, and 5,033,923 and WO 95/26258).
With the conventional tool holder, however, since the balancing means is attached to the flange of the holder body, the attached position of the balancing means to the holder body cannot be changed to an axial direction of the holder body. With such a tool holder as just described, although the position at which balancing in weight should be performed is different in the axial direction of the holder body depending upon a tool, since the adjusted position is a position fixed in the axial direction of the holder body, the tool holder cannot be applied to a tool which performs balancing at a different position.